This invention is related to a silent chain power transmitting device formed by a combination of a silent chain and sprocket. The silent chain is formed of a plurality of interleaved links. Each link has a pair of depending teeth joined at a crotch. Each tooth has an inside flank and an outside flank. The links are interleaved and are connected by connecting pins inserted through pin holes or apertures formed in each link. The teeth of the silent chain engage with teeth formed on an associated sprocket. In particular, this invention is related to a silent chain transmission device with reduced noise from impact engagement and vibration during operation.
Silent chain is typically used in automobiles, motorcycles and other vehicles to transmit power. The silent chain usually includes rows of multiple links interleaved in an endless loop wrapped around a pair of sprockets. During operation, one of the flank sides of the teeth on the link engages with the teeth on the sprocket to transmit power from the driving sprocket to the driven sprocket.
When using a conventional silent chain, engagement between the chain and the sprocket generates noise. In order to reduce noise, it is preferable to have smooth contact between the link and the sprocket. The engaging vibration or chordal action of the chain during engagement is also one of the causes of noise. In order to reduce the engaging vibration, the chain should maintain a linear movement until it engages with the sprocket. Therefore, it is believed that chain noise can be significantly reduced if the chain can maintain its linear movement and then smoothly engage with the sprocket.
In other words, the movement of the silent chain and the sprocket are very like the movement of a rack-type cutter. The linear part of the silent chain can be considered similar to a rack cutter that moves across a sprocket and the sprocket can be considered as the gear cut by the rack cutter.
Based on the above consideration, the inventor proposed a silent chain transmission device in Japanese laid-open application no. (Kokai) Hei 8-184348. In that silent chain, the flank side of the tooth on each link series which engages with a sprocket when the silent chain is extended in a linear form has the same shape as the part of the tooth shape of a rack cutter capable of generating the sprocket, and the sprocket has a tooth shape generated by such a rack cutter. As a result, the silent chain is able to maintain its linear movement and contact smoothly and then engage with the sprocket with minimal vibration during engagement.
By using such a silent chain transmission device, the noise generated by the impact of the chain on the sprocket and the engaging vibration, including the low-frequency noise, can be suppressed. In addition, since the rotation of the links within the link rows is proportional to the angle of rotation of the sprocket, the irregularity in angular velocity can be prevented.
In a series of studies on the reduction of the noise generated by a silent chain during operation it was found that the noise is generated not only in the initial stage of the engagement but also when the chain and the sprocket are fully engaged.
Especially for the silent chain with a structure using the inside flank for initial engagement but the outside flank for full engagement, the noise level reaches its peak when the chain and the sprocket are fully engaged. This may be explained by sudden increase of the load on the engaging point when the engaging point shifts from the inside flank to the outside flank.
However, the silent chain proposed in the prior art laid-open publication mentioned above has been designed to reduce the noise only in the initial stage of the engagement. The noise problem when the chain and the sprocket are fully engaged is not addressed by that chain.
In consideration of the situation described above, the purpose of this invention is to reduce the noise for a silent chain transmission device not only in the initial stage of the engagement but also when the chain and the sprocket are fully engaged, and to provide a silent chain with minimal vibration during engagement.